Is my step son harming my daughter?

Recently some odd occurrences happened. I have a camera monitor in her room and I woke up while she was still asleep and was just laying in bed with on my side facing a wall. My step son got up walked in our room to “check” to see if we were asleep and I wasn’t ready to get up. He didn’t say anything, or else I would’ve responded but assumed we were sleeping. So was my daughter. I rolled over because I heard him open her door and he grabbed her feet and dragged her from the one side of the crib to the other (I put her head near the end of the other becauee of the way the camera is I can see her face clearer) anyways then he went on to grabbing her by her hands and holding her in the air like her feet weren’t touching the bed (she’s 4 ish months) so I said can you put her down bud as she started getting upset and he said I am not touching her then I said again, can you please lay her back down and he denied it so I said back. I have the monitor on, I can see you. He then said “oh” n laid her back down. Later on, she was in her swing that rockers her and I ran out front quickly to do something. I could hear her start screaming bloody murder so I ran in and she was hanging completely off the swing and was unbuckled. Obviously my step son unbuckled her. But how did she end up hanging off the swing to the point her feet were flopping near the ground. Within two seconds she would’ve completely fallen out to hit her head off the hardwood floor. So why did he unstrap her, let her lay like that screaming? He was sitting on the couch 5 feet away when I came in and I found that so odd... why would he do that? Unbuckle her and pull her halfway out? She would’ve had to be sitting like that for a minute long as I heard her fussing but I figured she just lost soother and I’d be in in a short minute (taking out the recycling and garbage) I didn’t drop everything until I heard her scream. I am just confused on how come these things are happening? Am I overthinking that he could possibly be trying to hurt her or do these two examples sound odd to anybody as well? I also want to add, he hates his little brother (from mom) and says awful things about him to us. I don’t know why he hates him so much he just does!